Automatic dishwashing, particularly in domestic appliances, is an art very different from fabric laundering. Domestic fabric laundering is normally done in purpose-built machines having a tumbling action. These are very different from spray-action domestic automatic dishwashing appliances. The spray action in the latter tends to cause foam. Foam can easily overflow the low sills of domestic dishwashers and slow down the spray action, which in turn reduces the cleaning action. Thus in the distinct field of domestic machine dishwashing, the use of common foam-producing laundry detergent surfactants is normally restricted. These aspects are but a brief illustration of the unique formulation constraints in the domestic dishwashing field.
Automatic dishwashing with bleaching chemicals is different from fabric bleaching. In automatic dishwashing, use of bleaching chemicals involves promotion of soil removal from dishes, though soil bleaching may also occur. Additionally, soil antiredeposition and anti-spotting effects from bleaching chemicals are desirable. Some bleaching chemicals (such as a hydrogen peroxide source, alone or together with tetraacetylethylenediamine, aka "TAED") can, in certain circumstances, be helpful for cleaning dishware.
On account of the foregoing technical constraints as well as consumer needs and demands, automatic dishwashing detergent (ADD) compositions are undergoing continual change and improvement. Moreover environmental factors such as the restriction of phosphate, the desirability of providing ever-better cleaning results with less product, providing less thermal energy, and less water to assist the washing process, have all driven the need for improved ADD compositions.
In spite of such continuing changes to the formulation of ADD compositions, there continues to be a need for better cleaning ADD compositions, especially for removal of greasy soils. Typically, in other types of cleaning compositions such as laundry detergent compositions, cleaning improvements are continually being made by changing and improving the surfactants used. However, as noted hereinbefore, ADD compositions have the unique limitation of requiring very low sudsing compositions which is incompatible with most of the the surfactant systems and ingredients typically used in other cleaning compositions.
The exception is that low cloud point, low foaming nonionic surfactants have been used. But the cleaning performance therefrom has generally been very limited due to the requirement that low foaming nonionic surfactants are generally low cloud point nonionic surfactants, which have limited solubility in the wash solution. The lack of solubility of such nonionic surfactants greatly limits their cleaning ability, providing instead mainly spotting reduction benefits. Attempts at utilizing the more commonly used anionic surfactants have typically failed due to unacceptable foaming of such surfactants. Thus, there continues to be a need for ADD compositions containing surfactants which provide cleaning benefits (e.g., greasy soil removal benefits) without unacceptably high sudsing.
The present invention ADD composition comprising mixture of low cloud point nonionic surfactant and charged surfactant satisfy this long felt need. It is therefore an object of the present invention to provide ADD compositions comprising surfactant systems which provide cleaning benefits, especially greasy soil cleaning benefits (e.g., lipstick), while at the same time producing an acceptably low level of sudsing. These and other benefits of the present invention will be apparent from the detailed description which follows.